Silicon-based ultra-violet LED

ABSTRACT

A light emitting diode (LED), and a method for producing the same. The LED includes a substrate that may be made of silicon, a first conductive layer on one side, and a porous insulating layer on the opposite side. The insulating layer defines microcavities therein, the microcavities having sharp tips on their inner surfaces. The microcavities have gas inside. A second conductive layer is disposed over the insulating layer. When an electrical potential is applied between the conductive layers, the gas-filled microcavities act as plasma discharge lamps, emitting light. The light may be in the ultraviolet portion of the spectrum. The method includes etching a substrate to produce a porous insulating layer on one side, depositing a first conductive layer on the opposite side, and depositing a second conductive layer over the insulating layer. The microcavities in the insulating layer are then filled with gas.

BACKGROUND OF THE INVENTION

This application claims the benefit of U.S. Provisional Application No.60/364,683, filed Mar. 15, 2002 and entitled SILICON-BASED LIGHTEMITTING DIODE, which is in its entirety incorporated herewith byreference.

The invention relates to an apparatus and method for emitting light. Theinvention also relates more particularly to a silicon-basedlight-emitting diode for emitting light that may include wavelengths inthe ultraviolet portion of the electromagnetic spectrum.

Light emitting diodes, or LEDs, are known per se. Conventional LEDsutilize the semiconducting properties of materials such as silicon.

In a conventional LED, light is generated when free electrons drop fromthe conduction band of a semiconducting diode into energy holes. Eachsuch event releases energy in the form of a photon, with the wavelengthof the photon depending upon the energy gap between the conduction bandand the holes. As the energy gap becomes larger, the photons releasedlikewise become more energetic. The more energy an individual photonhas, the shorter its wavelength.

The principles governing the operation of conventional LEDs are wellknown, and are not further described herein.

However, known LEDs suffer from several limitations.

For example, the wavelengths that may be produced are limited by themagnitude of the energy gap. The shorter the wavelength of light that isto be emitted, the larger the energy gap must be. It is thereforeparticularly difficult to produce light with short wavelengths, inparticular ultraviolet light, using known LEDs. In principle, it ispossible to produce a semiconducting LED with an energy gap large enoughthat it emits ultraviolet light, i.e. light having a wavelength of lessthan about 400 nm. However, such LEDs are difficult to produce,expensive, and inefficient.

Indeed, silicon-based LEDs are extremely inefficient emitters of lightin general. The best reported efficiency for a silicon-based LED ofconventional design is 0.8%. That is, no more than 0.8% of the energyapplied to that LED is emitted as light, the remainder typically beinglost as heat.

SUMMARY OF THE INVENTION

It is the purpose of the present invention to overcome thesedifficulties, thereby providing an improved apparatus and method forgenerating light, including but not limited to ultraviolet light.

It is more particularly the purpose of the present invention to providean LED that is suited for producing light in wavelengths that mayinclude the ultraviolet portion of the electromagnetic spectrum, and amethod for producing the same.

An embodiment of an LED in accordance with the principles of the presentinvention includes a substrate. A first conductive layer is disposed ona first side of the substrate.

An insulating layer is disposed on a second side of the substrate. Theinsulating layer defines a plurality of microcavities therein. Themicrocavities have small points, referred to herein as asperites, ontheir surfaces. In addition, the microcavities contain gas therein.

A second conductive layer is disposed over the insulating layer. Thesecond conductive layer is transparent to radiation of the frequencythat the diode emits.

When an electrical potential is applied between the first conductivelayer and the second conductive layer, the microcavities in theinsulating layer act as tiny gas discharge lamps.

This occurs because the high electrical resistance of the insulatinglayer allows strong electric fields to develop within the microcavities.As these strong electric fields develop, the sharp tips of the asperitesbegin to eject electrons, ionizing the gas present in the microcavities.The gas transforms into plasma, which radiates light at one or moreplasma emission lines.

By controlling the physical properties of the device, i.e. thecomposition and pressure of the gas in the microcavities, it is possibleto control the frequency of the light emitted. For example, under theproper conditions, the light is in the ultraviolet portion of thespectrum.

It is emphasized that an LED in accordance with the principles of thepresent invention does not rely on semiconductive properties such aselectron transport.

It is furthermore emphasized that although particular embodiments of anLED in accordance with the principles of the claimed invention mayproduce ultraviolet light, the invention is not limited only toembodiments that produce ultraviolet light. Other embodiments mayproduce other wavelengths.

An LED in accordance with the principles of the present invention may beincorporated into an LED assembly.

An LED assembly in accordance with the principles of the presentinvention includes an LED, with an encapsulation enclosing it. Theencapsulation has a window that is transparent to the wavelength of thelight that is emitted by the LED. The assembly also includes first andsecond contact pins that are electrically connected to the first andsecond conductive layers. Thus, an electrical potential applied to thecontact pins causes an electrical potential to be applied to the firstand second conductive layers, so that the LED then emits light.

In a method for producing an LED in accordance with the principles ofthe present invention, a suitable substrate is provided. A firstconductive layer is applied to a first side of the substrate.

The second side of the substrate is etched to form an insulating layerwith microcavities therein, the microcavities having asperites.

A second conductive layer, transparent to radiation of the wavelengththat the LED is to produce, is applied over the insulating layer.

The microcavities are impregnated with gas.

An LED in accordance with the principles of the present invention may beincorporated into an LED assembly.

In a method for producing an LED assembly in accordance with theprinciples of the present invention, an LED is provided.

The LED is encapsulated with an encapsulation. The encapsulation has awindow that is transparent to radiation of the wavelength emitted by theLED.

A first contact pin is connected electrically to the first conductivelayer, and a second contact pin is connected electrically to the secondconductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Like reference numbers generally indicate corresponding elements in thefigures. Unless otherwise specified herein, these figures are not toscale.

FIG. 1 shows a schematic cross-section of an embodiment of a lightemitting diode in accordance with the principles of the presentinvention.

FIG. 2 shows an enlarged view of a microcavity of the LED shown in FIG.1.

FIG. 3 shows a schematic cross-section of an embodiment of an LEDassembly in accordance the principles of the present invention.

FIG. 4 shows an LED at a point in its production using a method inaccordance with the principles of the present invention.

FIG. 5 shows the LED of FIG. 4 at a later point in its production.

FIG. 6 shows the LED of FIG. 5 at a later point in its production.

FIG. 7 shows an embodiment of an arrangement for producing an insulatinglayer with microcavities therein in accordance with the principles ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an embodiment of an light emitting diode (LED) 10in accordance with the principles of the present invention is showntherein.

The LED 10 includes a substrate 12.

A first electrically conductive layer 14 is disposed on a first side ofthe substrate 12.

An electrically insulating layer 16 is disposed on a second side of thesubstrate 12, opposite the first conductive layer 14. The insulatinglayer 16 defines a plurality of tiny cavities therein, hereinafterreferred to as microcavities 18.

As illustrated in FIG. 2, the microcavities 18 include sharp tipstherein, hereinafter referred to as asperites 20.

Returning to FIG. 1, a second electrically conductive layer 22 isdisposed over the insulating layer 16.

The substrate 12 may be made from a variety of materials. In a preferredembodiment, the substrate 12 may comprise silicon. In a more preferredembodiment, the substrate 12 may comprise single-crystal silicon. In astill more preferred embodiment, the substrate 12 may comprise 100direction type n⁺ silicon. In a yet more preferred embodiment, thesubstrate 12 may be doped with antimony.

Such compositions are particularly suitable insofar as the use ofsilicon substrates in electronic devices is well-established andwell-understood. However, the above compositions are exemplary only. Awide variety of alternative materials may be equally suitable for use asthe substrate 12.

Substrates, in particular silicon substrates, are well known per se, andare not described further herein.

It is emphasized that although silicon is widely used for itssemiconductive properties, the present invention does not rely onsemiconduction, and does not require a substrate 12 that issemiconductive.

Rather, it is the classical resistance of the substrate 12 that is ofsignificance to the present invention. In a preferred embodiment, thesubstrate 12 has an electrical resistivity of 0.008 to 0.09 Ω-cm. Morepreferably, the substrate 12 has an electrical resistivity of 0.008 to0.02 Ω-cm.

The first conductive layer 14 may be made of any reasonably conductivematerial, including but not limited to metals and conductive polymers.In a preferred embodiment, the first conductive layer 14 comprisesaluminum. However, this is exemplary only, and other conductivematerials may be equally suitable.

The thickness of the first conductive layer 14 is sufficient to enablegood electrical conductivity. It will be appreciated by those of skillin the art that the precise thickness of the first conductive layer 14that is necessary depends on the material that is used for the firstconductive layer 14.

For example, when the first conductive layer 14 is composed of aluminumor a material with similar electrical properties, a thickness of 0.25 to1 μm may be sufficient for the first conductive layer 14. Morepreferably, the thickness may be 0.3 to 0.4 μm. However, thesethicknesses are exemplary only, and different thicknesses may be equallysuitable.

The insulating layer 16 comprises a material that is transparent tolight of the wavelength that is to be emitted by the LED 10. However,because the insulating layer 16 is porous, with a portion of its volumebeing microcavities 18, it may be suitable to use materials for theinsulating layer 16 that, when solid, would be poor transmitters oflight.

Like the substrate 12, the insulating layer 16 may be made from avariety of materials. In a preferred embodiment, the insulating layer 16may comprise silicon. In a more preferred embodiment, the insulatinglayer 16 may comprise single-crystal silicon. In a still more preferredembodiment, the insulating layer 16 may comprise 100 direction type n⁺silicon. In a yet more preferred embodiment, the insulating layer 16 maybe doped with antimony.

However, the above compositions are exemplary only. A wide variety ofalternative materials may be equally suitable for use as the insulatinglayer 16.

As noted with regard to the substrate 12, the present invention does notrely on semiconduction, and does not require an insulating layer 16 thatis semiconductive.

In a preferred embodiment, the insulating layer 16 is formed from thesame material as the substrate 12. In a more preferred embodiment, theinsulating layer 16 is formed from a portion of the substrate 12.

It will be appreciated by those of skill in the art that the precisethickness of the insulating layer 16 that is necessary depends on thematerial that is used for the insulating layer 16.

For example, when the insulating layer 16 is composed of silicon, athickness of 0.7 to 2.5 μm may be suitable for the insulating layer 16.More preferably, the thickness may be 1 to 2 μm. However, this thicknessis exemplary only, and different thicknesses may be equally suitable.

As noted above, the insulating layer 16 is porous, and defines aplurality of microcavities 18 therein.

For clarity, the microcavities 18 are illustrated in FIG. 1 as beingspherical, closed, and arranged in an orderly pattern. Although they areso illustrated for purposes of clarity, this is exemplary only.

It is not necessary for the microcavities 18 to be spherical. A varietyof other shapes, including but not limited to cylinders or tubes, andamorphous “blobs”, may be equally suitable. It is also noted thatdifferent microcavities 18 may have different shapes within the sameinsulating layer 16.

Likewise, it is not necessary for the microcavities 18 to be closed offfrom one another. Microcavities 18 that are interconnected may beequally suitable.

Furthermore, it is not necessary for the microcavities 18 to bedistributed in a regular or orderly pattern. For certain embodiments itis preferable that the microcavities 18 are spread in a substantiallyuniform manner across the area of the insulating layer 16. However, arandom or chaotic distribution of microcavities 18 within the insulatinglayer 16 may be equally suitable as an ordered arrangement.

As may be seen in FIG. 2, the microcavities 18 include asperites 20therein. The asperites 20 are sharp tips on the surfaces of themicrocavities 18.

As illustrated, the asperites 20 are discrete, conical points. However,this is exemplary only. A wide variety of shapes of asperites 20 may beequally suitable. It is only necessary that they include some relativelysharp edge or point, so as to facilitate the discharge of an electricfield as described below.

Likewise, it is not necessary that each microcavity 18 contain exactlytwo asperites 20, or that asperites 20 be arranged at opposite ends of amicrocavity 18. Although this arrangement is illustrated for clarity, itis exemplary only, and other numbers and arrangements of asperites 20may be equally suitable.

The microcavities 18 have a gas therein. The gas is one that is suitablefor producing light via a plasma discharge when an electric currentflows therethrough.

A wide variety of gases are suitable for use in the present invention.Suitable gases include, but are not limited to, nitrogen, xenon, andargon. The gases need not be pure; mixtures of two or more gases mayalso be suitable.

A variety of pressures of gas within the microcavities 18 may besuitable. The pressure of the gas depends at least in part upon thespecific physical properties of the embodiment of the LED 10 inquestion, i.e. the type of gas used, the size, shape, and distributionof microcavities 18 and asperites 20, the dimensions, composition, andresistivity of the insulating layer 16, etc.

For example, for certain preferred embodiments, a gas pressure of 1 to100 mbar of nitrogen is suitable. However, this is exemplary only, andother gas pressures may be equally suitable.

Referring again to FIG. 1, the second conductive layer 22 may be made ofany reasonably conductive material, including but not limited to metalsand conductive polymers. In a preferred embodiment, the secondconductive layer 22 comprises an alloy of gold and copper. In a morepreferred embodiment, the second conductive layer 22 comprises an alloyof gold and copper in a ratio of 9:1 to 3:2. In a still more preferredembodiment, the second conductive layer 22 comprises an alloy of goldand copper in a ratio of 4:1 to 7:3. However, this is exemplary only,and other conductive materials may be equally suitable.

The thickness of the second conductive layer 22 is sufficient to enablegood electrical conductivity. It will be appreciated by those of skillin the art that the precise thickness of the second conductive layer 22that is necessary depends on the material that is used for the secondconductive layer 22.

The second conductive layer 22 is transparent to light of the wavelengththat is to be emitted by the LED. For certain materials, including butnot limited to metals, this requirement may also help determine thesuitable thickness of the second conductive layer 22.

For example, when the second conductive layer 22 is composed of an alloyof gold and copper in a ratio of 4:1 to 7:3 or a material with similarelectrical and optical properties, a thickness of 20 to 100 nm may besuitable for the second conductive layer 22. More preferably, thethickness may be 30 to 60 nm. It is noted that the gold and copper alloyin question is transparent to certain wavelengths of light, includingultraviolet light, when applied in these thicknesses. However, thesethicknesses are exemplary only, and different thicknesses may be equallysuitable.

When an electrical potential is applied between the first and secondconductive layers 14 and 22, the relatively high resistivity of theinsulating layer 16 prevents the free flow of current therebetween. Thisresults in the growth of strong electric fields within the insulatinglayer 16.

In particular, strong electric fields form within the microcavities 18.If the microcavities 18 were generally smooth, the electric fields mighteventually stabilize. However, the sharp tips of the asperites 20 withinthe microcavities 18 results in local discontinuities in the electricfields. At some point, the electric fields in a given microcavity 18collapse, whereupon the asperites 20 therein inject streams of electronsfrom their sharp tips into the microcavity 18.

This sudden electrical discharge ionizes the gas within the microcavity18 into a plasma by stripping away one or more electrons from the gasatoms. When the freed electrons in the plasma recombine with the gasatoms, the gases emit radiation at characteristic wavelengths thatdepend upon the type of gas present in the microcavity.

For example, for nitrogen, radiation with a wavelength of approximately337.1 nm is emitted. It is noted that this wavelength is in theultraviolet portion of the electromagnetic spectrum. However, this isexemplary only, and embodiments of the present invention that emit otherwavelengths may be equally suitable. In particular, embodiments thatproduce one or more wavelengths of ultraviolet radiation between 200 and400 nm may be equally suitable. Embodiments that produce light at one ormore wavelengths that are not in the ultraviolet portion of theelectromagnetic spectrum may also be equally suitable.

So long as an electrical potential continues to be applied, the electricfield within the microcavity 18 will regenerate after each collapse, andthe process will repeat.

In other words, the microcavities 18 act as a plurality of tiny plasmadischarge lamps. The operational principles of plasma discharge lampsare well known per se, and are not described further herein.

It is noted that the various microcavities 18 will not necessarilydischarge in unison, nor is it necessary that they do so. Furthermore,it is not even necessary that all of the microcavities 18 that arepresent within a given insulating layer 16 discharge at all, so long asat least some do so.

The electric potential between the first and second conductive layers 14and 22 is sufficient to generate electric fields that build and collapsein at least a significant portion of the microcavities 18. In apreferred embodiment, the electric potential may need be no more thanapproximately 20 volts. In a more preferred embodiment, the electricpotential may need be no more than approximately 10 volts.

Turning to FIG. 3, an embodiment of an LED assembly 30 in accordancewith the principles of the present invention is shown therein.

The LED assembly 30 includes an LED in accordance with the principles ofthe claimed invention, similar to the LED 10 shown in FIG. 1.

The LED assembly thus includes a substrate 12, a first electricallyconductive layer 14 is disposed on a first side of the substrate 12, andan electrically insulating layer 16 is disposed on a second side of thesubstrate 12. The insulating layer 16 defines a plurality ofmicrocavities 18 therein, with asperites 20. A second electricallyconductive layer 22 is disposed over the insulating layer 16.

In addition, the LED assembly 30 includes an encapsulation 32, whichencapsulates the substrate 12, first electrically conductive layer 14,electrically insulating layer 16, and second electrically conductivelayer 22.

The encapsulation 32 includes a window 34 that is transparent to lightof the wavelength that the LED emits.

The encapsulation 32 encapsulates the LED, both to protect the LED, andalso to protect persons or structures that come in contact with it fromdamage that might be caused by electric potential, plasma emission, etc.

In addition, certain embodiments of encapsulation 32 may act as abarrier between the microcavities 18 and the outside atmosphere, inorder to reduce any exchange of gas between the atmosphere and themicrocavities 18 that might degrade the performance of the LED. In thoseembodiments, the encapsulation may be gas-tight.

The LED assembly 30 also includes a first contact pin 36 that is inelectrical contact with the first conductive layer 14, and a secondcontact pin 38 that is in contact with the second conductive layer 22.

Thus, an electrical potential that is applied between the first andsecond contact pins 36 and 38 results in a similar electrical potentialbeing applied between the first conductive layer 14 and the secondconductive layer 22.

It is emphasized that incorporating the LED 10 previously shown anddescribed into the LED assembly 30 is exemplary only. For certainapplications, it may be equally suitable to incorporate an LED 10 inaccordance with the principles of the present invention into otherassemblies, or to use it as a stand-alone device.

A variety of materials may be suitable for use as the encapsulation 32.Suitable materials include, but are not limited to, plastics.

A variety of materials likewise may be suitable for use as the window34. Suitable materials include, but are not limited to, glasstransparent to light of the wavelength emitted by the LED.

Similarly, a variety of materials may be suitable for use as the firstand second contact pins 36 and 38. In a preferred embodiment, the firstand second contact pins 36 and 38 are made of metal wire. However, thisis exemplary only, and other materials may be equally suitable.

It is noted that, although only two contact pins 36 and 38 are shown, itmay be equally suitable for certain embodiments to include additionalcontact pins.

As illustrated in FIG. 3, the second contact pin 38 passes through thefirst conductive layer 14, the substrate 12, and the insulating layer 16to reach the second conductive layer 22. As shown, in order to preventshort circuits (i.e. between the second contact pin 38 and the firstconductive layer 14), the LED assembly 30 may include insulation 40 toisolate the second contact pin 38.

However, this is exemplary only. For certain embodiments, it may not benecessary to use insulation 40 to isolate the second contact pin 38. Forexample, the second contact pin 38 may be connected to the secondconductive layer 22 in such a way that it does not contact the firstconductive layer 14. One exemplary arrangement is to connect the secondcontact pin 38 directly to the second conductive layer 22 withoutpassing through other portions of the LED. Another exemplary arrangementis to prepare an aperture in the first conductive layer 14 proximate thelocation of the second contact pin 38, so as to avoid contacttherebetween. Other embodiments may likewise be suitable.

FIGS. 4-6 show an LED similar to the LED 10 illustrated in FIG. 1, atseveral points in an exemplary production process.

As shown in FIG. 4, the exemplary process begins with a substrate 12.Methods for producing substrates, in particular silicon substrates, arewell known per se, and are not described further herein.

As shown in FIG. 5, an insulating layer 16 is then formed on thesubstrate 12. The insulating layer has microcavities 18 and asperites 20therein.

As may be seen from a comparison of FIGS. 4 and 5, in the exemplaryprocess illustrated therein the insulating layer 16 is formed from aportion of the substrate 12. However, this is exemplary only, and othermethods, including but not limited to forming an insulating layer 16separately and applying it to the substrate 12, may be equally suitable.

One exemplary method for producing the insulating layer 16 with themicrocavities 18 and the asperites 20 therein is to electrochemicallyetch the substrate 12, so as to render a portion of the substrate 12porous.

Referring to FIG. 7, an exemplary arrangement for electrochemicallyetching the substrate 12 is shown therein.

As illustrated in FIG. 7, the substrate 14 with the first conductivelayer 12 disposed therein is placed in a bath of etchant 50.

The substrate 14 is connected electrically to a power supply 54. Asshown, the substrate is connected to the positive terminal of the powersupply 54, and so acts as the anode.

A cathode 52 is also placed in the etchant 50, and is connected to thenegative terminal of the power supply 54. In order to facilitatemonitoring of the etching process, an ammeter 52 may be connectedbetween the cathode 52 and the power supply 54. However, this isexemplary only.

The composition of the cathode depends at least in part on the etchingconditions and the type of etchant 50 used. For example, a platinumcathode is suitable for many types of electrochemical etchingoperations, as it is highly conductive, heat tolerant, and highlyresistant to corrosion. However, this is exemplary only, and other typesof cathode may be equally suitable.

A variety of etchants 50 and etching conditions may be suitable forperforming electrochemical etching of the substrate 12. It will beappreciated by those of skill in the art that the particular conditionsand etchants 50 will vary depending on such factors as the material usedto form the substrate 12.

For example, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may use an etchant 50 comprising anethanoic hydrogen fluoride solution. In a more preferred embodiment, theetchant might have a concentration of 10% to 25%. In a still morepreferred embodiment, the etchant might have a concentration of 24%.

Likewise, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may include etching with a current densityof 1 to 4 mA/cm². In a more preferred embodiment, the current densitymay be 2 mA/cm².

Similarly, for a substrate 12 comprised of silicon, a preferredembodiment of an etching step may last for from 5 to 30 minutes. In amore preferred embodiment, etching may last for from 10 to 15 minutes.

In addition, for certain embodiments, it may be preferable to apply aresist to some or all of the substrate 12, and/or any other elements ofthe LED 10 that are present during etching in order to control theportions that are etched.

However, these parameters are exemplary only, and other etchants andother etching conditions may be equally suitable.

Furthermore, the use of an electrochemical etching step is itselfexemplary only. Other steps for producing an insulating layer 16 withmicrocavities 18 and asperites 20 therein may be equally suitable.

In some embodiments of a method according to the principles of thepresent invention wherein the insulating layer 16 is formed by etchingthe substrate 12, it may be preferable to heat the substrate 12 prior toetching in order to drive off impurities within or on the surface of thesubstrate 12 that might interfere with etching.

For example, for certain embodiments, heating the substrate 12 to atemperature of 200 to 300° C., for a duration of 30±6 minutes may besuitable. Furthermore, for certain embodiments, heating the substrate 12while it is in a vacuum may also be suitable.

However, heating the substrate prior to etching is exemplary only.

As shown in FIG. 6, a first conductive layer 14 is then applied to afirst side of the substrate 12.

A variety of methods may be used to apply the first conductive layer 14to the substrate 12. It will be appreciated by those of skill in the artthat the methods suitable for applying the first conductive layer 14depend at least in part on the particular materials used in the firstconductive layer 14.

For example, when the first conductive layer 14 is composed of aluminum,suitable methods may include, but are not limited to, electroplating,vapor deposition, and sputtering. These methods are exemplary only, anddifferent methods may be equally suitable.

In addition, in the exemplary method described herein, a secondconductive layer 22 is formed over the insulating layer 16.

A variety of methods may be used to apply the second conductive layer 22to the insulating layer 16. It will be appreciated by those of skill inthe art that the methods suitable for applying the second conductivelayer 22 depend at least in part on the particular materials used in thesecond conductive layer 22.

For example, when the second conductive layer 22 is composed of an alloyof gold and copper, suitable methods may include, but are not limitedto, electroplating, vapor deposition, and sputtering. These methods areexemplary only, and different methods may be equally suitable.

When the second conductive layer 22 is applied, the resulting LEDresembles that illustrated in FIG. 1.

According to this exemplary method, once the solid structure of the LEDis complete, gas is introduced into the microcavities 18.

A variety of methods may be used to introduce gas into the microcavities18. For example, for certain embodiments, impregnating the microcavities18 by surrounding the LED with gas may be suitable. In a preferredembodiment, the microcavities 18 are impregnated to a pressure of 1 to100 mbar for a duration of 30±6 minutes.

In addition, in certain embodiments of the method it may be suitable toheat the LED while impregnating the microcavities 18 with gas. In apreferred embodiment, the LED is heated to 100 to 150° C. whileimpregnating the microcavities 18 with gas.

However, these conditions and methods for introducing gas into themicrocavities are exemplary only. Other conditions and other methods maybe equally suitable.

It is noted that, although FIGS. 4-6 and the preceding text provide adescription of an exemplary method of producing an LED that is inaccordance with the principles of the claimed invention, this method,and in particular the order of the steps as described, is exemplaryonly.

For example, although the addition of the first conductive layer isdescribed after the addition of the insulating layer, for certainembodiments it may be equally suitable to form the insulating layerafter forming the first conductive layer.

Thus, the order of the steps as described is exemplary only, and otherarrangements may be equally suitable.

A method of producing an LED assembly in accordance with the principlesof the present invention may be used to produce an LED 30 similar tothat shown in FIG. 3.

An LED having a substrate 12, a first electrically conductive layer 14,an electrically insulating layer 16 with a plurality of microcavities 18and asperites 20 therein, and a second electrically conductive layer 22is encapsulated in an encapsulation 32.

The encapsulation 32 includes a window 34 that is transparent toradiation of the wavelengths produced by the LED.

A variety of methods of forming the encapsulation 32 and the window 34may be suitable.

A first contact pin 36 is connected electrically with the firstconductive layer 14, and a second contact pin 38 is connectedelectrically with the second conductive layer 22, so that an electricalpotential applied between the first and second contact pins 36 and 38produces a similar electrical potential between the first conductivelayer 14 and the second conductive layer 22.

A variety of methods of connecting the first and second contact pins 36and 38 may be suitable. Suitable methods include, but are not limitedto, the use of a conductive adhesive between a contact pin 36, 38 andits corresponding conductive layer 14, 22.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. A light emitting diode, comprising: a substrate; a firstconductive layer disposed on a first side of said substrate; aninsulating layer disposed on a second side of said substrate, saidinsulating layer defining a plurality of microcavities therein, saidcavities comprising asperites, said microcavities having a gas therein;and a second conductive layer disposed on said insulating layer; whereinwhen an electrical potential is applied between said first conductivelayer and said second conductive layer, said gas forms a plasma thatemits radiation in the electromagnetic spectrum; and said secondconductive layer is transparent to said radiation.
 2. The light emittingdiode according to claim 1, wherein: said substrate comprises silicon.3. The light emitting diode according to claim 2, wherein: saidsubstrate is doped with antimony.
 4. The light emitting diode accordingto claim 2, wherein: said substrate comprises silicon (100), type n⁺. 5.The light emitting diode according to claim 1, wherein: said substratehas a resistivity of 0.008 to 0.09 Ω-cm.
 6. The light emitting diodeaccording to claim 1, wherein: said substrate has a resistivity of 0.008to 0.02 Ω-cm.
 7. The light emitting diode according to claim 1, wherein:said first conductive layer comprises metal.
 8. The light emitting diodeaccording to claim 7, wherein: said first conductive layer comprisesaluminum.
 9. The light emitting diode according to claim 1, wherein:said first conductive layer has a thickness of 0.25 to 1 μm.
 10. Thelight emitting diode according to claim 1, wherein: said firstconductive layer has a thickness of 0.3 to 0.4 μm.
 11. The lightemitting diode according to claim 1, wherein: said insulating layercomprises silicon.
 12. The light emitting diode according to claim 11,wherein: said insulating layer is doped with antimony.
 13. The lightemitting diode according to claim 11, wherein: said insulating layercomprises silicon (100), type n⁺.
 14. The light emitting diode accordingto claim 1, wherein: said insulating layer has a resistivity of 0.008 to0.09 Ω-cm.
 15. The light emitting diode according to claim 1, wherein:said insulating layer has a resistivity of 0.008 to 0.02 Ω-cm.
 16. Thelight emitting diode according to claim 1, wherein: said insulatinglayer and said substrate comprise identical materials.
 17. The lightemitting diode according to claim 1, wherein: said insulating layer hasa thickness of 0.7 to 2.5 μm.
 18. The light emitting diode according toclaim 1, wherein: said insulating layer has a thickness of 1 to 2 μm.19. The light emitting diode according to claim 1, wherein: said gas insaid microcavities comprises at least one of the group consisting ofnitrogen, xenon, and argon.
 20. The light emitting diode according toclaim 1, wherein: said gas in said microcavities has a pressure of 1 to100 mbar.
 21. The light emitting diode according to claim 1, wherein:said second conductive layer comprises metal.
 22. The light emittingdiode according to claim 21, wherein: said second conductive layercomprises an alloy of gold and copper.
 23. The light emitting diodeaccording to claim 22, wherein: said alloy has a gold:copper ratio of9:1 to 3:2.
 24. The light emitting diode according to claim 22, wherein:said alloy has a gold:copper ratio of 4:1 to 7:3.
 25. The light emittingdiode according to claim 1, wherein: said second conductive layer has athickness of 20 to 100 nm.
 26. The light emitting diode according toclaim 1, wherein: said second conductive layer has a thickness of 30 to60 nm.
 27. The light emitting diode according to claim 1, wherein: saidelectrical potential is not more than approximately 20 volts.
 28. Thelight emitting diode according to claim 1, wherein: said electricalpotential is not more than approximately 10 volts.
 29. The lightemitting diode according to claim 1, wherein: said radiation has awavelength of 200 to 400 nm.
 30. The light emitting diode according toclaim 1, wherein: said radiation has a wavelength of 337.1 nm.
 31. AnLED assembly, comprising: a light emitting diode, said diode comprising:a substrate; a first conductive layer disposed on a first side of saidsubstrate; an insulating layer disposed on a second side of saidsubstrate, said insulating layer defining a plurality of microcavitiestherein, said cavities comprising asperites, said microcavities having agas therein; and a second conductive layer disposed on said insulatinglayer; wherein when an electrical potential is applied between saidfirst conductive layer and said second conductive layer, said gas formsa plasma that emits radiation in the electromagnetic spectrum; and saidsecond conductive layer is transparent to said radiation; anencapsulation encapsulating said diode, said encapsulation comprising awindow transparent to said radiation; and first and second contact pins,said first contact pin being in electrical contact with said firstconductive layer, and said second contact pin being in electricalcontact with said second conductive layer.
 32. The LED assemblyaccording to claim 31, wherein: said encapsulation is gas-tight.
 33. TheLED assembly according to claim 31, wherein: said window is transparentto radiation between 200 and 400 nm in wavelength.
 34. The LED assemblyaccording to claim 31, wherein: said window has a transmittance of atleast 90%.
 35. The LED assembly according to claim 31, wherein: saidcontact pins are bonded to said conductive layers with conductiveadhesive.